The present invention relates to a liquid crystal display device driven by a multiplexed signal which is the output from a two-frequency matrix-addressing circuit. The device includes a twisted nematic liquid crystal display element incorporating a liquid crystal material having a dielectric anisotropy which is frequency-dependent. The composition and the liquid crystal display device are constructed for operating in the TN-mode, well known to those skilled in the art. Also, the composition may contain a dichroic dye in a Guest-Host relationship, the mode of operation being referred to as PGH.
Such liquid crystal display elements are now broadly used as digital displays in electronic desk calculators, wristwatches and the like. Where it is necessary to produce the display consisting of many picture cells or elements, as, for example, the XY matrix display, it is a precondition to adopt multiplex driving because of the necessity to decrease the number of terminals which must be electrically connected with the driving circuit and so as to simplify the driving circuit itself. Moreover, it is essential to use AC drive in order to lengthen the life of the liquid crystal material. Multiplex driving of a liquid crystal display element is now termed the generalized AC amplitude-selective multiplexing method.
While a number of such constructions are now known, difficulties are encountered, principally with respect to contrast and with respect to establishing and maintaining suitable voltage levels for turning the display ON and OFF. The present invention is designed to eliminate these difficulties.